1. The Field of the Invention
This invention relates to computer systems, telecommunication networks, and switches therefor and, more particularly, to novel systems and methods for switching and processing photonic information.
2. Background Discussion
Multiplexing is a method for transmitting multiple, distinct signals over a single physical carrier medium. Much of the protocol of computer hardware deals with the encoding and decoding of signals according to some time scheme for maintaining signal integrity and uniqueness from other signals. In conventional time-division types of multiplexing, signals are transmitted within specific time slots or burst positions. In order to prevent individual bits from being transmitted at the same time, each burst of bits may be encoded into a signal and transmitted over the carrier medium at a specific time.
As transmission rates increase, the individual time divisions available for each small quantity of information in a signal are reduced. However, with the advent of photonic processing, the transmission, encoding, and decoding of photonic signals taken from the electromagnetic spectrum, deserve further consideration. In conventional computer systems, as well as conventional telecommunications networks, the switching, routing, and transmission of signals throughout networks and between processors or processes may be a major limiting factor in performance. Typically, transmissions of a signal require encoding of the signal in a carrier medium, according to a protocol or format.
Thereafter, transmission occurs as a physical phenomenon in which light, or other electromagnetic radiation, electrical signals, mechanical transmissions, or the like are transferred between a source and a destination. At the destination, a decoder must then manipulate the physical response to the incoming signals, thus reconstructing original data encoded by the sender. Communications in general may include communications between individual machines. Machines may be network-aware, hardware of any variety, individual computers, individual components within computers, and the like.
Thus, the issue of sending and receiving information or message traffic is of major consequence in virtually all aspects of industrial and commercial equipment and devices in the information age. Whether communications involve sending and receiving information between machines, or telecommunications of data signals, audio signals, voice, or the like over conventional telecommunications networks, the sending and receiving requirements of rapidly encoding and decoding are present.
With the advent of photonic signals and photonic signal processing, new speed limits are being approached by transmission media. Moreover, origination of signals can now be executed literally at light speeds. Accordingly, what is needed is a system for multiplexing photonic signals over photonic carrier media in such a way as to maximize speed, while maintaining the integrity of information.
To be most useful, communications and switching equipment must interface with data channels from a plethora of sources. An ability to transmit and redirect multiple channels simultaneously and independently, increases the capacity and usefulness of transmission, multiplexing and switching equipment Over the years several standard methods have been developed for packing multiple channels onto a single transmission medium. In optical frequency division multiplexing (OFDM) and wavelength division multiplexing (WDM), each channel has a unique wavelength which typically remains constant with time. In spread spectrum systems, all channels may have substantially the same average wavelength with short term variations that are unique to each channel. Typically, sets of orthogonal functions are used to define channel wavelengths. In most systems and applications, it may be desirable that the wavelength of each channel can be described as a function of time, distinct and unique from all other channels. An ability to wavelength shift photonic signals from one channel, whose wavelength can be defined as a function of time, into any other channel would facilitate the transmission, multiplexing and switching of an extremely wide range of photonic signals.
One dilemma in engineering photonic systems is the conversion of signals or information between the electronic and photonic domains. Photonic systems are capable of high transmission rates and distances. Computers and control equipment are typically electronic due to their flexibility, low cost and wide availability. Typically, switching and multiplexing require the conversion of optical signals into electrical signals for processing and control, followed by reconversion into the optical domain for further transmission. An ability to direct and control a photonic stream of data with electronic devices and systems without requiring conversion of the photonic data stream to the electronic domain would leverage the best characteristics of each domain.
While it may be desirable to leave data in the photonic domain when transmitting, multiplexing and switching photonic signals, it is often desirable to encode an electronic data signal onto an existing carrier without additional complexity and cost. An ability to process photonic or electronic data signals with the same mechanism would simplify interfacing with a wide range of communications, process control, and computational equipment.
One difficulty in interfacing a wide variety of photonic equipment is the assignment of channel wavelengths and encoding techniques. Setup and configuration become problematic. An ability to automatically channelize (change the wavelength of a photonic carrier to a given channel) and transparently pass along a data encoded photonic stream across a network of photonic equipment without prior knowledge of the channel wavelengths and encoding techniques would reduce the cost and complexity of deploying photonic equipment.
Another issue in photonic transmission systems is carrier wavelength variability due to component variability, temperature drift, system jitter and other factors. Carrier wavelength variability makes it difficult to densely pack channels onto a transmission medium without collisions occurring, especially when multiplexing channels from multiple sources. Typically, expensive, temperature-compensated, reference lasers or light sources are required to stabilize a photonic signal. Most state-of-the-art photonic transmission systems require conversion to the electronic domain followed by remodulation of a light source and retransmission in order to eliminate any jitter introduced during transmission. An ability to compensate for wavelength variability of existing photonic streams without remodulation and retransmission would increase the capacity and lower the cost of transmission, multiplexing and switching equipment.
In view of the foregoing, it is a primary objective of the present invention to provide a method and apparatus for transmitting, multiplexing and switching photonic signals without requiring conversion to the electronic domain. It is also a primary objective of the present invention to provide a method and apparatus for embedding electronic data signals onto existing photonic carriers and signals.
One objective of the invention is to provide a system that facilitates the transmission, multiplexing and switching of an extremely wide range of photonic signals. It is also an objective of the invention to provide a system for multiplexing photonic signals over photonic carrier media in such a way as to maximize speed, while maintaining the integrity of information. Another objective of the invention is the ability to interface with data channels from a plethora of sources, to transmit and redirect those data channels simultaneously and independently. In particular it is desired to wavelength shift photonic signals from one channel, whose wavelength can be defined as a function of time, into any other channel without requiring conversion to and reconversion from the electronic domain. It is also an objective of the invention to automatically channelize and transparently pass along a data encoded photonic stream across a network of photonic equipment without prior knowledge of the channel wavelengths or encoding methods and to compensate for wavelength variability of existing photonic streams without retransmission.
The present invention uses various embodiments to wavelength shift photonic signals. Wavelength shifting is also applied as a mechansim to multiplex, switching and transmit photonic signals. In certain embodiments in accordance with the invention, an apparatus for wavelength shifting uses modulation techniques to change photonic carrier wavelengths. Modulation techniques may be selected to be appropriate to a modulation device of choice. A particular modulation device may be driven by a modulation synthesizer producing a controlling waveform optimized for the device.
Consistent with the foregoing objectives, and in accordance with the invention as embodied and broadly described herein, an apparatus and method are disclosed, in suitable detail to enable one of ordinary skill in the art to make and use the invention.